The invention relates to temperature sensors, particularly those in which a change in resistance of a material is used as an indication of temperature.
There are a number of different types of resistive temperature sensors commercially available. These include thermocouples, thermistors, and resistance temperature detectors (RTD's). Thermocouples and RTD's are relatively expensive to manufacture and only have moderate sensitivity. Thermistors alone have high sensitivity, but are non-linear in response, only moderately accurate, have part-to-part variations, and therefore are not suitable for many applications.
Temperature sensors can also be constructed from thermistors by combining them together with discrete resistors in a bridge circuit. Such manufacturing procedure is expensive since the thermistors must be individually tested and matched with discrete resistors having specific resistance values. The resulting discrete circuit is not compact and does not have the mechanical and electrical reliability required for many applications. Prior to the present invention there has been no low cost, compact, highly accurate, reliable temperature sensor.